In dry etch apparatuses and processes, one or more plasmas are caused to interact with suitably prepared surfaces of semiconductor or other materials to form one or more intended microstructures thereon. In one form of dry etch apparatus, the plasmas are controllably produced by two electrodes in a diode configuration, and in another form of dry etch apparatus, the plasmas are controllably produced by three electrodes in a triode or other three-electrode configuration. Selected etches corresponding to the intended microstructures being fabricated are effected by varying the applied electrode powers and relative spacings, and by varying the gas chemistries and other plasma control parameters, in a manner well known to those skilled in the art.
One important etch known to those skilled in the art is intended to allow its subsequent metallization as a contact or via. The smaller the dimensions of these contact holes and vias are to be, the more difficult it becomes to provide acceptable metallization. For physical dimensions of about a micron and less, typically called for in VLSI and other applications, the profiles of these etches must be carefully controlled or the subsequent metallization is subject to undesirable microcracking and metal fatigue that adversely impact the reliability of the contacts or vias.
An etch having a so-called "champagne" profile is able to provide microcracking-free contacts and vias when subsequently metallized, and such an etch has been produced by different dry etch apparatuses by a variety of different processes. In an article entitled "Contact Hole and Via Profiling by High Rate Isotropic and Anisotropic Etching of Oxides", by Grewal et al., appearing in the proceedings of an IEEE V-MIC Conference (June 1987), incorporated herein by reference, the use of a single wafer etcher from LAM-Research having electrodes in a diode configuration is reported to implement a two-step isotropic/anisotropic etch process to form such champagne profiles, and the use of the LAM-Research single wafer etcher to implement an isotropic etch followed by the use of an Applied Materials RIE hex etcher to implement an anisotropic etch is also reported to form these champagne profiles. For the two-step etch process implemented in the LAM-Research single wafer etcher, the electrode gap and gas chemistries were varied to first implement the isotropic step and then the anisotropic step. The gas chemistries for the isotropic etch were carbon tetrafluoride (CF.sub.4) and oxygen (O.sub.2), and the gas chemistries for the anisotropic etch implemented in the LAM-Research etcher and in the Applied Materials RIE hex etcher were a trifluoromethane (CHF.sub.3) and oxygen (O.sub.2) mixture.
In an article entitled "Silicon Dioxide Profile Control for Contacts and Vias", by Giffen et al., appearing at Solid State Technology (April 1989), incorporated herein by reference, the use of a Tegal 1513e single wafer etcher having top, side and bottom electrodes in a three-electrode configuration is reported to provide such champagne profiles. In one process mode reported therein, the wafer rests on the bottom electrode, which is powered, the side electrode is at floating potential, and the top electrode is grounded. Radio frequency (RF) power is pulsed to the bottom electrode for segregating ions and radicals in the induced plasma discharge, thereby etching photoresist isotropically while anisotropical1y etching oxide. In another reported process mode, the three electrodes are powered in such a manner that the oxide layer first is etched isotropically by powering the side electrode while holding the wafer electrode at floating potential, and then etched anisotropically. In the pulsed power process mode, the duty cycle, which controls the ratio of the anisotropic to the isotropic etch, controls the oxide slope, and nitrogen trifluoride (NF.sub.3) was the primary etchant reported. For the isotropic/anisotropic process mode, different chemistries were used for the different tri-electrode RF power configurations, NF.sub.3 for the isotropic etch and SF.sub.6 /CHF.sub.3 for the anisotropic etch.
In an article entitled "Isotropic Plasma Etching of Doped and Undoped Silicon Dioxide for Contact Holes and Vias", by W. G. M. van den Hoek et al., appearing at J. Vac. Sci. Technol. A7 (3), (May/June 1989), incorporated herein by reference, the use of a Matrix System One etcher having two chambers separated by a grounded aluminum grid to implement an isotropic etch followed by the use of an AME 8110 hexode reactor to implement an anisotropic etch are reported for providing such champagne profiles. The isotropic etch in the Matrix System One etcher uses He and NF.sub.3 gas chemistries, and the AME 8110 hexode reactor uses CHF.sub.3 /CO.sub.2 /He gas chemistries.
Other diode and triode reactors are known, such as the model "384"diode reactor commercially available from the instant assignee, and the Waferetch 606/616 triode reactor, commercially available from GCA Corporation.
The utility of these heretofore known dry etch machines and/or processes has been limited either by an inability to form champagne profiles, or the etches that have been able to be formed thereby have suffered from less than desirable reproduceability, critical dimension control and/or, among others, resist erosion.